1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus each having the electrophotographic photosensitive member.
2. Description of the Related Art
Among the electrophotographic photosensitive member, an electrophotographic photosensitive member using an organic photoconductive material has good film formability and can be produced by coating. Therefore, it has an advantage of high productivity.
The electrophotographic photosensitive member generally has a support and a photosensitive layer formed on the support, and in the photosensitive layer, a charge generating material and a hole transport material are used. Further, an undercoat layer is frequently provided between the support and the photosensitive layer for the purpose of suppressing charge injection from the support to the photosensitive layer side and occurrence of image defects such as black spots.
In recent years, a charge generating material having higher sensitivity has been used. However, as the charge generating material has higher sensitivity, the amount of charge generated is increased. Therefore, the charge easily stagnates in the photosensitive layer, and positive ghosting is easily generated. The positive ghosting is a phenomenon in which the density of only the portion irradiated with light at the prior rotation becomes deep while forming one sheet of the image.
As a technique of suppressing such positive ghosting, Japanese Patent Application Laid-Open No. 2007-148294, Japanese Patent Application Laid-Open No. 2008-250082, National Publication of International Patent Application No. 2009-505156, and Japanese Patent Application Laid-Open No. 2008-65173 each describe a technique of allowing an electron transport material to be contained in an undercoat layer. These patents further describe a technique of curing the undercoat layer so that, when an electron transport material is allowed to be contained in an undercoat layer, the electron transport material may not be eluted into a solvent in a coating liquid for a photosensitive layer during the formation of a photosensitive layer which is the upper layer of the undercoat layer.
In recent years, requirements for the quality of electrophotographic images have been increasing, and the tolerance to the positive ghosting as described above has become significantly severe.
As a result of investigations by the inventors, it has been found that the techniques described in the above literatures still have room for improvement with respect to the suppression (reduction) of positive ghosting, particularly the variation of the positive ghosting level before and after continuous image output.